1. Field of the Invention
The present invention relates to a disc apparatus having a disc with servo information written thereon and a method of writing servo patterns on the disc, and more particularly, to a disc apparatus that itself is capable of writing the servo information (i.e., that has a self-servowrite capability) and a servo pattern write method thereof.
2. Description of the Related Art
Precision improvement in positioning a write head at the time of self-servowrite is indispensable for writing detailed servo information. Conventional arts related to the positioning of a read head necessary for positioning a write head include those described in Japanese Patent Laid-open Application No. Hei. 10-50014 (Patent document 1), Japanese Patent Laid-open Application No. 2002-319253 (Patent document 2), and Japanese Patent Laid-open Application No. 2002-288956 (Patent document 3).
Patent document 1 and Patent document 2 disclose methods of weighted-averaging a plurality of servo bursts (propagation patterns) in order to obtain a position error signal of a read head. Besides, another art of writing an auxiliary burst signal for self-servowrite is disclosed. Patent document 3 discloses that servo information written on a front surface and that written on a rear surface are deviated from each other in a radial direction by an amount equal to one fourth of a track width.
[Patent document 1] Japanese Patent Laid-open Application No. Hei 10-50014 (FIG. 11, paragraphs 0041 to 0043, FIG. 14, paragraph 0044)
[Patent document 2] Japanese Patent Laid-open Application No. 2002-319253
[Patent document 3] Japanese Patent Laid-open Application No. 2002-288956 (FIG. 9, paragraph 0082)
The methods disclosed in Patent documents 1, 2 are thought to have a drawback in view of positioning precision of the read head since it is sometimes unavoidable to detect the position error signal near a dynamic range saturation point of the output thereof at the time of the positioning of the read head. This precision affects positioning precision of the write head. The method of writing the auxiliary burst signal is also thought to have a drawback in view of write efficiency because it requires an increased time and labor. Further, Patent document 3 does not teach in its disclosed contents what measure should be taken to solve the situation that the radial direction interval between the read/write heads changes depending on the radial direction position.